Emergency Dose Estimation Using Optically Stimulated Luminescence from Human Tooth Enamel

Human teeth were studied for potential use as emergency Optically Stimulated Luminescence (OSL) dosimeters. By using multiple-teeth samples in combination with a custom-built sensitive OSL reader, (60)Co-equivalent doses below 0.64 Gy were measured immediately after exposure with the lowest value being 27 mGy for the most sensitive sample. The variability of OSL sensitivity, from individual to individual using multiple-teeth samples, was determined to be 53%. X-ray and beta exposure were found to produce OSL curves with the same shape that differed from those due to ultraviolet (UV) exposure; as a result, correlation was observed between OSL signals after X-ray and beta exposure and was absent if compared to OSL signals after UV exposure. Fading of the OSL signal was "typical" for most teeth with just a few of incisors showing atypical behavior. Typical fading dependences were described by a bi-exponential decay function with "fast" (decay time around of 12 min) and "slow" (decay time about 14 h) components. OSL detection limits, based on the techniques developed to-date, were found to be satisfactory from the point-of-view of medical triage requirements if conducted within 24 hours of the exposure.     

热释光和光释光发光谱的测量

介绍了自行研制的计算机化热释光和光释光三维光谱测量装置的系统结构及其工作原理.在计算机的控制下,通过精密加热器或激发光源以热激发或光激发的方式使样品发光.从样品发出的光经过光路和光栅分光系统后,形成光谱,被高灵敏度的CCD采集,再将光谱图像模拟信号变为可以直接用计算机进行数据处理的数据信号.波长范围200~800nm,波长分辨率优于2nm,人机界面友好,操作方便.利用热释光和光释光三维光谱测量装置测量了SrSO₄:Eu(0.1%,摩尔分数)和CaSO₄:Eu(0.1%,摩尔分数)的光释光发光谱和热释光发光谱,得到SrSO₄:Eu的光释光发光波长与热释光发光波长均为375nm,而CaSO₄:Eu的光释光发光波长与热释光发光波长均为385nm,说明热释光和光释光具有相同的发光中心,均来自于Eu²⁺的能级跃迁.同时在CaSO₄:Eu的热释光发光谱中还观察到了Eu³⁺的发光.与二维发光曲线相比较,通过对三维热释光和光释光发光谱的研究,可以得到更丰富的信息,这有助于对热释光和光释光发光机制进行更深入的研究.     

Study of Optically Stimulated Luminescence of LiF:Mg,Ti for beta and gamma dosimetry

Modern advances in radiation medicine – radiodiagnosis, radiotherapy and interventional radiography – each present dosimetry challenges for the medical physicist that did not exist previously. In all of these areas a constant balance has to be made between the treatment necessary to destroy the tumor and the unnecessary exposure of healthy tissue. Innovative applications of OSL dosimetry are now appearing in each of these areas to help the medical physicist and oncologist design the most effective, and least deleterious, treatment for their patients. High sensitivity, precise delivery of light, fast readout times, simpler readers and easier automation are the main advantages of OSL in comparison with TLD.This work aimed to study the application of OSL technique using lithium fluoride dosimeters doped with magnesium and titanium (LiF:Mg,Ti) for application in beta and gamma dosimetry.     

Temporal Characteristics of Luminescencefrom Ultrashort-pulsed Infrared LaserStimulated Electron Trapping Materials

l.IntroductionElectrontrappingmaterials(ETMIs)areakindofinfraredstimulatedstoragephos-phors[lj.Thesephosphorscanstoreenergyafterexposuretovisibleorultravio1etlight.Beingsubeequentlystimu1atedbyinfraredIight,thestoredenergycanbereIeasedintheformofvisiblelight.Recently,thesematerialshaveshowninestimablepromiseforuseinopticalcomputingandopticalinformationprocessingbecauseoftheirgreatsensitivity,highspatialresolution,largelineardynamicrangeandhighsignal-to-nosie-ratio(SNR)[z~ej.Inreal-timeinfo…     

Optically Activated Luminescence in a Natural Quartz

The spectral and kinetic characteristics of some natural quartz samples were studied by the method of optically stimulated afterglow. Defects with an unusually long time of luminescence decay of intracenter type ( = 179 msec, = 450 msec) have been revealed. Some of the parameters of these centers (stimulation and luminescence spectra, kinetics of afterglow decay, EPR spectrum, their temperature dependences, and also the stable behavior of these centers on exposure to thermal and optical effects) have been determined. Their role in the appearance of a luminescence signal ineffaceable in the process of formation of geological deposits and the possible processes leading to the afterglow of these centers are discussed.     

两种磷光材料在聚合物掺杂体系中的发光特性研究

磷光材料由于可以利用电致激发所形成的单重态和三重态激子,因而可以得到接近100%的内量子效率。文章对常温下基于磷光材料Ir(ppy)₃及Ir(piq)₃掺杂PVK薄膜为发光层的器件的光学和电学特性进行了研究。光致发光的结果显示相同掺杂质量比下由PVK到Ir(piq)₃的能量传递比到Ir(ppy)₃更加困难。通过研究两种掺杂体系不同质量比的电致发光特性,可以认为这两种磷光器件的发光主要来自于磷光客体分子直接俘获载流子发光而非主体的能量传递。Ir(piq)₃掺杂体系对掺杂比例的依赖更为明显,从能级结构分析,认为是由于Ir(piq)₃的更低的HOMO及高的LUMO能级,而比Ir(ppy)₃具有更好的载流子俘获和传输特性。     

PDP用发光材料的研究进展

目前,商用PDP三基色荧光粉主要为红色(Y,Gd)BO₃:Eu³⁺,绿色Zn₂SiO₄:Mn²⁺、BaAl₁₂O₁₉:Mn²⁺或(Gd, Y)BO₃:Tb³⁺,蓝色BaMgAl₁₀O₁₇:Eu²⁺。然而,以上3种荧光粉均存在发光效率低的问题;另外,(Y, Gd)BO₃:Eu³⁺的色纯度较差,Zn₂SiO₄:Mn²⁺和BaAl₁₂O₁₉:Mn²⁺的衰减时间较长,(Gd,Y)BO₃:Tb³⁺亮度不足,BaMgAl₁₀O₁₇:Eu²⁺的稳定性较差,这些因素在一定程度上制约了其发光和显示性能。本文总结了目前红、绿、蓝三种发光材料的真空紫外发光机理以及发光性能改进的研究进展,同时,对目前开发新型PDP用发光材料的研究也进行了介绍。     

Anti-Stokes Luminescence in Carbon Materials

Optics and Spectroscopy - The laser-induced emission of carbon materials is studied experimentally. We observed broadband emission spectra in the visible region, as well as a red shift of the...     

Two-Photon Excited Luminescence of NV-Centers and Stimulated Raman Scattering in Nanodiamonds

Journal of Russian Laser Research - In this study, zero-phonon line (ZPL) at 638 nm associated with multiphoton excited negatively-charged single nitrogen-vacancy (NV)-center luminescence is...     

基于受激布里渊散射的新型多级慢光延时结构的研究

设计了一种基于受激布里渊散射(SBS)的新型多级慢光延时结构.该多级延时结构将两段慢光延时介质用两个环形器相连接,使经过一级延时后剩余的抽运光经过环形器进入到第二段慢光延时介质中作为二级延时的抽运.该结构与传统的多级慢光延时结构相比,不需要为每段延时介质提供独立的抽运系统,结构简单,抽运光利用率高,延时效果显著.实验选...     

Study of the Thermoluminescence and Optical Stimulated Luminescence properties of quartz crystal

Abstract

Thermoluminescence (TL) and Optical Stimulated Luminescence (OSL) of natural quartz crystals from sediments have been studied in order to obtain the ages of the sediments' deposition. The sediments were collected from an archaeological site, located in State of Mato Grosso do Sul, Brazil. In the present work the phototransfer TL process was observed in the 394°C TL peak, which increased 10–20% in its intensity when the sample was exposed to sunlight. As the samples did not provide a residual TL, a new methodology to evaluate the paleodose (P) was devised. Annual doses were evaluated based on uranium, thorium and potassium contents determined by neutron activation analysis. Preliminary ages were compared to those obtained by OSL and ages between (11–35) 10³ BP were obtained.     

Luminescence and Stimulated Emission in Zinc Oxide Nanoparticles,Films, and Crystals

ZnO has attracted attention as a candidate material for ultraviolet light-emitting devices. Its 3.37 -eV band gap is comparable to that of GaN, and single crystal substrates can be grown. Control of p-type conductivity in ZnO is under study in several laboratories including ours. We report streak camera measurements of time-resolved luminescence and stimulated emission excited in single crystal, film, and particle samples under excitation by 300 fs laser pulses at temperatures from 17 K to 295 K. We also describe p-n junctions formed by control of oxygen pressure in reactive sputtering of ZnO films, and results of introducing nitrogen during reactive sputtering.     

Gamma-Ray and Neutron Dosimetry Using Semiconductor Silicon Diodes

Radiation response to gamma-ray absorbed dose in the range of 10 to 750 kGy and neutron absorbed dose in the range of 10 mGy to 700 Gy were investigated using Swedish manufactured silicon diode, type 5422. The results indicated that its sensitivity to gamma-rays is 17.6 m V/kGY up to 60 kGy, and its sensitivity reduces to 10-17 mV/kGy from 70 kGy up to 700 kGy within an error of ±7%, while its response to fast fission neutrons is G7 mV/Gy. Factors affecting dosimeter reading such as dosimeter reading at high temperature, dosimeter annealing and reusability are also studied. The system teas used for gamma-ray and neutron dosimetry around high level gamma-ray source, reactor ducted concrete shield, and it is also examined for reactor core dosimetry.     

TE-TM Mode Converter Using Optically Active Polymer

A novel TE-TM mode converter using optically active polymer: poly-1-menthylmethacrylate (PMtMA) was studied theoretically and experimentally. In a three-layered slab waveguide consisting of the PMtMA core layer on a fused quartz substrate, a low-loss TE₀-TM₀ mode conversion with an efficiency of 60 to 70% was easily obtained for the first time at a wavelength of 441.6 nm. The method to achieve a phase-matched operation of this polymer TE-TM mode converter was also discussed.     

All-Fiber Ultra-Fast Switching Using Stimulated Raman Scattering

We propose a method for all-fiber ultra-fast switching using stimulated Raman scattering. It is based on the transference of energy from the signal as pump to the control signal as first Stokes by stimulated Raman scattering. In the absence of a control signal, the transference of energy from the pump signal to the generated first Stokes is negligible, which results in high output power at the pump signal wavelength. To minimize the walk-off problem between two wavelengths, we chose pump signal and control signal to be equally spaced on opposite sides of the zero dispersion wavelength of the fiber. Based on this assumption, the all-fiber ultra-fast optical switch with low power consumption and high output extinction ratio can be realized.     

Taking Account of the Nonstationarity in Analyzing the Optically Stimulated Electron Emission of Irradiated Dielectrics

The distortions of the optically stimulated electron emission (OSEE) spectra resulting from the exponential decay in the recording time have been analyzed. It has been shown that taking account of the emission current nonstationary in analyzing the emission spectra permits obtaining isochronal temperature dependences of intensity for selective OSEE bands. The procedure for calculating the quantum yield of the OSEE and the activation barriers of thermal ionization of the excited states of defects is described. Analysis of the photoemission kinetics permits estimating the concentration of active OSEE centers with unknown parameters (optical transition oscillator strength, quantum yield). For diamagnetic oxygen-deficient centers in glassy SiO₂, the photoemission kinetics has been calculated and the thermal ionization barrier of the photoexcited singlet state and the quantum yield of the OSEE have been determined. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 5, pp. 615–621, September–October, 2005.     

Lanthanide Luminescence as a Probe of Nanocrystalline Materials

The sharp lines in the optical spectra of lanthanide ions in solids are sensitive to the local environment surrounding the ion and, therefore, provide a local probe to study new materials. This paper reports the laser spectroscopic characterization of a series of Eu₂O₃ nanocrystals, which serve as a model compound for understanding the spectroscopy of lanthanides in nanocrystalline materials. The optical spectra of Eu₂O₃ particles with diameters of approximately 18 to 4 nm show an increase in inhomogeneous broadening and a transition to a very disordered phase as the particle size decreases. The ⁵D₀ fluorescence transients of the nanocrystals are shorter than in bulk material show no clear trend as a function of particle size but do become single exponential for 6- and 4-nm particles.     

Bistable Optically Writable Image Memory Using Optical Feedback

A novel, parallel aligned optically addressed liquid crystal spatial light modulator has been used to implement an optically writable image memory. The memory uses a two-beam interferometer with optical feedback which exhibits thresholding, hysteresis, and bistability. We discuss the characteristics of the system, and present the results of an experimental demonstration.Presented at the International Commission for Optics Topical Meeting, Kyoto, 1994.     

Dosimetry Methods of Fast Neutron Using the Semiconductor Diodes

Semiconductor detectors based on a silicon pin diode are frequently used in the detection of different nuclear radiations. For the detection and dosimetry of fast neutrons, these silicon detectors are coupled with a fast neutron converter. Incident neutrons interact with the converter and produce charged particles that can deposit their energy in the detectors and produce a signal. In this study, three methods are introduced for fast neutron dosimetry by using the silicon detectors, which are： recoil proton spectroscopy, similarity of detector response function with conversion function, and a discriminator layer. Monte Carlo simulation is used to calculate the response of dosimetry systems based on these methods. In the different doses of an 241Am-Be neutron source, dosimetry responses are evaluated. The error values of measured data for dosimetry by these methods are in the range of 15-25%. We find fairly good agreement in the 241Am-Be neutron sources.     

All-Fiber Optical Signal Inversion Using Stimulated Raman Scattering

We propose a method for all-optical signal inversion by means of stimulated Raman scattering (SRS). The idea is based on the transference of energy from the logic state #x201C;1#x201D; to the second stokes and making the logic state #x201C;0#x201D; into logic state #x201C;1#x201D; by receiving energy from the pump through SRS. According to the numerical simulation, a continuous wave pump source of LOW at 1453 nm and a few hundred meters of highly nonlinear fiber are required to invert an input signal at 1555 nm. The optical signal is inverted with high on-off contrast ratio.